In general ABI compatibility is not guaranteed, but we do strive for it in the core packages. I’d recommend letting the upstream package know of the ABI breakage (nodelet_core in this case?), though once it’s released there’s not much to be done about it other than break ABI again to go to the old state.
Since ABI stability is not guaranteed, especially for non-core packages, I think it’s best not to assume you can have deb’s on top of ours that do not need to be rebuilt after a sync.